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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 0 |
| 2 | 4 |
| 3 | 48 |
| 4 | 464 |
| 5 | 4480 |
| 6 | 48448 |
| 7 | 621824 |
| 8 | 9320704 |
| 9 | 154890240 |
| 10 | 2746131456 |
| 11 | 51237908480 |
| 12 | 1007228375040 |
| 13 | 20965557829632 |
| 14 | 463091379159040 |
| 15 | 10826828061147136 |
| 16 | 266438312153120768 |
| 17 | 6861616219559034880 |
| 18 | 184128217520198123520 |
| 19 | 5135753969867535941632 |
[1,0,4,48,464,4480,48448,621824,9320704,154890240, 2746131456,51237908480,1007228375040, 20965557829632,463091379159040,10826828061147136, 266438312153120768,6861616219559034880, 184128217520198123520,5135753969867535941632] |